Downhole drilling motor having an improved shaft seal



Jan. 23,l 1968 M. D. CARLETON 3,365,202

DOWNHOLE DRILLING MOTOR HAVING AN IMPROVED SHAFT SEAL Filed June l5,1965 2 Sheets-Sheet 1 Zik W i W M il, WfmRP .,mam/ wr Z fw., f a ,m 5.@f, v www //W 7 //A////////// ////K i v \CXC m \w M www s 4 s FLM Arrow/wJan. 23, 1968 M, D. CARU-:TON

DOWNHOLE DRILLING MOTOR HAVING AN IMPROVED SHAFT SEAL 2 Sheets-Sheet 2Filed June 1 5, 1965 United States Patent O 3,35,2tl2 DGWNHLE DRlLLlNGMOTR HAVING AN IMPRUVED SHAFT SEAL Mike D. Carleton, deceased, late ofFranklin, Tex., by Ida H. Carleton, administratriur, Franklin, Tex.,assigner to Dresser Industries, Inc., Dallas, Tex.

Filed .lune 15, 1965, Ser. No. 464,244 6 Claims. (Cl. 277-73) ABSTRACT FTHE DISCLOSURE The seal disclosed herein is adapted uniquely for a fluiddriven motor to prevent the flow of fluid past the motor in the tubularmeans within which such motor usually is positioned. An annularpiston-like member is moveable between two surfaces and having a surfaceexposed to the driving fluid within such tubular means to urge theannular piston against one of the surfaces. For fluid flow in theopposite direction, the annular piston is moveable against the oppositesurface to permit the fluid to flow therepast readily.

This invention relates to a downhole drilling motor having an improvedfluid flow seal that substantially prevents escape of power fluid fromthe lower end of the motor housing which surrounds the rotating outputshaft.

This invention is adaptable to a variety of fluid driven downholedrilling motors wherein a shaft carrying the bit is rotated by means ofhydraulic energy supplied to it from the well surface. The most commonlyused form of hydraulically driven downhole motor is the turbodrill andfor the purpose of illustrating this invention, the drawings anddescriptive matter relate to turbodrills although the invention isadaptable to other forms of downhole motors.

Conventional fluid driven downhole motors utilize a lower radial bearingto absorb lateral forces between the rotating output shaft and the motorhousing during drilling operations. The bearing frequently includes anelastomer sleeve element carried by the housing and engaging the shaft.The sleeve is provided with a plurality of longitudinal grooves on itsinner surface to permit circulation fluid to flow through the bearing tolubricate and cool the bearing contact surfaces and prevent seizure. Itis important to prevent this circulation fluid from flowing out into thebore hole from the annulus between the output shaft and the motorhousing. Any fluid which thus escapes does not pass downwardly throughthe output shaft to be Vdischarged through the bit thereby reducing theamount of fluid available to remove formation cuttings away from the`working edges of the bit and prevent a build-up of cuttings in thebottom of the hole. Also, the escape of this fluid through the lowerradial bearing into the bore hole appreciably reduces the availablepressure differential across the bit which it is important to maintainfor drilling efficiency.

Various devices have been suggested in the past for sealing between therotating output shaft and the relatively stationary motor housing at apoint below the radial bearing. These have not been altogethersuccessful for various reasons including the failure to meet tworequirements for creating and maintaining an effective seal duringdrilling operations. One requirement is that the seal must be maintainedregardless of the degree of wear on the vertical thrust bearings in themotor. Not only do the vertical thrust bearings have a certain degree ofassembly clearance which permits relative longitudinal movement betweenthe shaft and the housing but also as they wear, additional clearance iscreated permitting an even greater degree of longitudinal movement.Second, the seal must be maintained regardless of the clearance andradial wear on the lower radial bearing.

3,365,202 Patented Jan. 23, 1968 ice It is an object of this inventionto provide a fluid operated downhole drilling motor with an improvedseal for the output shaft of the motor.

It is another object to provide such a motor with a seal that canaccommodate the lateral `and longitudinal movement of the shaft thatresults from the wear of the thrust and radial bearings of the motor.

It is another object to provide such a seal that will bypass fluid asthe motor is being lowered into the well bore and which can do sowithout being damage-d by the forces exerted thereon by the fluid whenthe motor is being lowered rapidly.

It is another object to provide such a seal that has a minimum ofcavities in which cuttings and other solid ma. terial can collect andinterfere with the operation of the seal.

These and other objects, advantages, and features of the invention willbe apparent to those skilled in the art from a consideration of thisspecification, the claims and the attached drawings.

In the drawings:

FIG. 1 is a view, partly in vertical section and partly in elevation, ofthe lower portion of a turbodrill equipped with the preferred embodimentof the shaft seal of this invention;

FIG. 2 is `an enlarged view in vertical section of the shaft seal s-hownin FIG. l; and

FIGS. 3 and 4 are vertical sectional views showing alternatearrangements of shaft seals.

Turbodrill 10 is arranged to drive bit 11 attached to its hollow outputshaft 12. The illustrated turbodrill contains a plurality of turbinestages 14 (only the lower portion of one stage is shown), verticalthrust bearings 15, lower radial bearing 16, and shaft seal 17, varioussections of the turbodrill housing, the latter generally being numbered18. It is the purpose of the thrust bearings 1S to resist the downwardforce imposed on the rotor shaft by the drilling fluid acting againstthe turbine rotor blades. The thrust bearings v15 also transmit to theshaft and the bit the drilling weight imposed on the housing by thedrill string (not shown).

Below the thrust bearings is located radial bearing subassembly -16which supports the output shaft in the lower end of housing 18. In theembodiment shown in FIG. 2, this radial bearing subassembly includesbearing bushing 19 located inhousing section 18a and engaging bearingsleeve 20 carried by the hollow shaft and keyed thereto by key 21. Thebearing bushing is formed of an elastomer such as rubber 16a and isreinforced with steel backing 16h. The bearing Ebushing haslongitudinally extending grooves 16C on its inner surface to allow thepassage of fluid across the face of the bearing. Seal 22 prevents theflow of drilling fluid between sleeve 20 and shaft 12.

For a more complete description of a turbodrill of this type shown, seeU.S. Patent No. 3,519,222.

Both the lantern ring 23 and shaft are provided with an opening 24through which the drilling fluid can enter the output shaft after it haspassed through the turbine sections and thrust lbearings 1S. The fluidthen flows through the output shaft to bit 11. Unless prevented fromdoing so, at least a portion of this fluid would flow through thegrooves 16e across radial bearing 16 and out of the turbodrill throughthe annulus defined by the output shaft and the tubular means comprisinghousing sections 18a and 18b. A substantial amount of the fluid wouldfollow this path because normally there is a substantial pressure dropacross the bit. The loss of a substantial amount of this fluid into thebore hole annulus at this point would greatly reduce the ability of thedrilling fluid to cool the bit and to remove the cuttings therefrom.

Therefore, in accordance with this invention, an irnproved shaft seal 17is provided to prevent the drilling fluid from flowing from theturbodrill through the aforesaid annulus. As shown in FIG. 2, the sealcomprises a first annular member 25 mounted on the output shaft. Thisannular member is provided with an annular groove in which is located anannular ring of elastomeric material 26 to provide an upwardly facingsealing surface. The annular member 25 is prevented from movinglongitudinally of the shaft by shoulder 2'7 on shaft l2 and the lowerend of bearing sleeve 2@ which is held against rotation relative to theshaft by key 2l which also locks member 2S to shaft 12.

Also encircling the shaft is a second annular member or piston 28 whichhas a downwardly facing sealing surface formed by annular ring 29 ofhard, abrasive, resistant material, such as Stellite. The piston isspaced from shaft 12 to permit the shaft to move laterally or to wobbleto the extent allowed by any wear which may occur in the radial bearingssupporting the shaft. Also, the piston is movable longitudinally so itcan follow any longitudinal movement of sealing face 26 relative tohousing member 18b due to thrust bearing wear. The piston is keyed tohousing section 18b by key 3l) so it is held against rotation relativethereto. Seal means, comprising in this embodiment O-rings 31, arepositioned between the piston and housing section 18a. With thisarrangement, the upper end of the piston provides an upwardly facingsurface against which the fiuid in the annulus 32 can act to urge thepiston downwardly to in turn urge the sealing surfaces 26 and 29together to effect a seal. As the pressure in the annulus increases, theforce urging the two sealing surfaces together likewise increases. Theupwardly facing area of the piston should be suiiiciently large that thetwo sealing surfaces are engaged tightly enough to substantially preventflow therebetween. On the other hand, the area should not be so large asto press the two sealing surfaces together so tightly that excessivewear results. In this connection, a small amount of leakage may bedesirable to not only permit some flow past the radial bearing 16 butalso to lubricate and cool the sealing surfaces 26 and 29. In caseadditional flow is desired past the radial bearings, an opening 33 canbe provided in the bearing sleeve and hollow shaft.

It is desirable to be able to lower the turbodrill into a well borefilled with drilling mud at a reasonable rate. This causes force to beexerted upwardly upon the piston and, therefore, the piston must Ibedesigned to resist this force without being damaged. In the embodimentshown in FIG. 2, the piston being movable longitudinally, will moveupwardly away from the seal member 25 when subjected to an upward surgeof pressure. Thus, the seal will open and allow iluid to flow throughthe annulus between the outside diameter of the bearing sleeve and theinner diameter of the piston 28 and thence upwardly into the turbodrill.This is desirable since it provides another path for the fluid beingdisplaced thereby tending to reduce the upward force exerted on thepiston. The upward movement of the piston must be limited however.Therefore housing section 18a is provided with downwardly facingshoulder 34 and piston 23 is provided with an upwardly facing annularshoulder 3S which engages shoulder 34 to limit the upward travel of thepiston. By this arrangement, the key 3l) is not placed in shear in anupward direction and the shoulders 34 and 35, being on the outside ofthe piston, can be made of relatively large area so as to distribute theforces exerted on them.

Since there is relative rotation between the seal surfaces 26 and 29,they will wear. As explained above, one sealing surface is provided by aresilient sealing ring 26 and the other sealing surface by a hard wearresistant material 29, such as Stellite. In this way the rubber suffersthe major portion of wear, but it can be quickly, easily, andeconomically replaced when necessary.

FIGS. 3 and 4 show alternate ways of assembling the seal. In bothembodiments, the construction of the components of the seal are modifiedsomewhat. However, the operating principle and function of thecomponents are the same as described above.

FIG. 3 illustrates the arrangement where the housing for the seal andthe radial bearing are integrally connected together. This is done whenthe radial bearing comprises a one piece body 36 of rubber bonded to theinner surface of the housing. Also, in this embodiment, the firstannular mem-ber 25 is held in position on output shaft l2 by a pluralityof set screws 42, only one of which is shown, rather than a shoulder onthe shaft, as was the case in the first embodiment` Thus to change theseal 26', all that is necessary is to take out the set screws 42 andthen slide member 25' off the lower end of shaft 12. This eliminates theneed to remove all of the parts of the turbodrill above the seal as mustbe done when the meinber 25 of FIG. 2 is to be replaced.

In the embodiment shown in FIG. 4, lower housing section 13b is threadedto the outside of housing section 18a. Since the same type radialbearing 36 is used in this embodiment as in FIG. 3, housing section 18hdoes not need to hold the bearing against longitudinal movement withinthe housing 18a and therefore it can be threadedly connected to thehousing by threads provided on the eX- terior of the housing as shown.The construction of the seal otherwise is the same as shown in FIGS. 1and 2.

From the foregoing, it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which lare obvious and which are inherentto the apparatus.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. In a downholedrilling motor having an output shaft rotated by a drilling fluid drivenmotor and tubular means connected to the motor and extending down tosurround said shaft thereby forming a fluid passage between said tubularmeans and said output shaft, seal means for substantially preventingflow of fluid out of the motor through said iiuid passage, said sealmeans comprising means on one of the output shaft and tubular meansproviding a first endwise facing annular sealing surface, an annularmember carried by and longitudinally movable with respect to the otherof the output shaft and tubular means and providing a second endwisefacing annular sealing surface opposing and slidingly engageable withthe first sealing surface, said annular member being of a size so as toprovide a radial space to permit the shaft to move laterally, saidannular member having an upwardly facing surface exposed to fluid withinsaid tubular means and of an area sufficient that the pressure 0f suchfluid is effective to urge the annular member longitudinally toward thefirst sealing surface to thereby cause said sealing surfaces to engageand substantially prevent the flow of fluid from the motor through saidfluid passage, and interengageable stop means on the annular member andtubular means to limit the distance said member can move longitudinallyaway from said first sealing surface.

2. In a downhole drilling motor having an output shaft rotated by adrilling fluid driven motor and tubular means connected to the motor andextending down to surround said shaft thereby forming a fluid passagebetween said tubular means and said output shaft, seal means forsubstantialiy preventing flow of fluid out of the motor through saidfluid passage, said seal means comprising means on the output shaftproviding an endwise facing annular sealing surface, and an annularmember carried by and longitudinally movable with respect to the tubularmeans and having an endwise facing annular sealing surface opposing andslidingly engageable with the sealing surface on the output shaft, saidannular member being larger than the output shaft so as to be spacedradially therefrom to permit the shaft to move late-rally, said annularmember having an upwardly facing surface exposed to fluid within saidtubular means and of an area sufficient that the pressure of such fluidis effective to urge the annular member longitudinally toward thesealing surface on the output shaft to thereby cause said sealingsurfaces to engage and substantially prevent the flow of fluid from themotor through said fluid passage.

3. In a downhole drilling motor having a hollow output shaft rotated bya drilling fluid driven motor and tubular means connected to the motorand extending down to surround said shaft thereby forming a fluidpassage between said tubular means and said output shaft, seal means forsubstantially preventing flow of fluid out of the motor through saidfluid passage, said seal means comprising a first annular memberencircling the output shaft and attached thereto and having an endwisefacing annular sealing surface, a second annular member carried by thetubular means for longitudinal movement relative thereto and providedwith an endwise facing annular sealing surface opposing the sealingsurface on the first member, said second member being larger than theoutput shaft so as to be spaced radially therefrom to permit the shaftto move laterally, said second member having an upwardly facing surfaceexposed to fluid within said tubular means and of an area sufficientthat the pressure of such fluid is effective to urge the second memberlongitudinally toward the first member to thereby cause their sealingsurfaces to engage and substantially prevent the flow of fluid from themotor through said fluid passage, and interengageable stop means on thesecond member and tubular means to limit the distance said second membercan move longitudinally away from the first member.

4. In a downhole drilling motor having a hollow output shaft rotated bya drilling fluid driven motor and tubular means connected to the motorand extending down to surround said shaft thereby forming a fluidpassage between said tubular means and said output shaft, seal means forsubstantially preventing flow of fluid out of the motor through saidfluid passage, said seal means comprising an annular member encirclingthe output shaft and attached thereto and having an upwardly facingsealing surface, an annular piston disposed within the tubular means andsurrounding the output shaft, means carried by the tubular meansmounting the piston for longitudinal movement relative thereto butlimiting relative rotation, said piston having a downwardly facingannular sealing surface opposing the sealing surface on the firstmember, said piston being larger than the output shaft so as to bespaced radially therefrom to permit the shaft to move laterally, saidpiston having its upper end exposed to fluid within said tubular meansand of an area sufficient that the pressure of such fluid is effectiveto urge the piston longitudinally toward the first member to therebycause said sealing surfaces to engage and substantially prevent the flowof fluid from the motor through said fluid passage, and interengageablestop means on the piston and tubular means to limit the distance saidpiston can move longitudinally away from the first member.

5. In a downhole drilling motor having an output shaft rotated by adrilling fluid driven motor and tubular means connected to the motor andextending down to surround said shaft thereby forming a fluid passagebetween said tubular means and said output shaft, seal means forsubstantially preventing flow of fluid out of the motor through saidfluid passage, said seal means comprising a first annular member havinga bore of such size that the first member can be slid over the outputshaft toward said tubular means, means releasably connecting the firstmember to the output shaft, said first member having an endwise facingannular sealing surface, and a second annular member carried by thetubular means for longitudinal movement relative thereto and providedwith an endwise facing annular sealing surface opposing the sealingsurface on the first member, said second member being larger than theoutput shaft so as to be spaced radially therefrom to permit the shaftto move laterally, said second member having an upwardly facing surfaceeX- posed to fluid within said tubular means and of an area sufficientthat the pressure of such fluid is effective to urge the second memberlongitudinally toward the first member to thereby cause their sealingsurfaces to engage and substantially prevent the flow of fluid from themotor through said fluid passage.

6. The apparatus of claim 5 wherein said first members sealing surfacecomprises a replaceable ring having a resilient surface whereby suchring can be replaced by releasing the connecting means and sliding therst member off the output shaft.

References Cited UNITED STATES PATENTS SAMUEL ROTHBERG, PrimaryExaminer.

UNITED STATES PATENT OFFICE CERTUHCATE 0F CORRECT1ON Patent No.3,365,202 January Z3, 1968 Mike D. Carleton, deceased by Ida H.Carleton,

adminstratrx It s certified that error appears in the above identifiedpatent and that said Letters Patent are hereby corrected as shown below:

column 2, line 55, for "3,519,222" read 3,159,222

Signed and sealed this 29th day of July 1969.

(SEAlJ ttestz Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR.

